JP2011215648A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a warm-up period and enable stable fixing, in a fixing device such as a copying machine including a fixing member which circulates and moves on a circular locus, a support member located inside the fixing member and supporting it, a pressure member which presses the fixing member, and a heater which heats the fixing member.SOLUTION: A backup member (106) for backing up the support member is provided on the back of the support member (104). Also, a heat insulation member (108) is interposed between the backup member (106) and support member (104).

Description

  The present invention relates to a fixing device used for fixing a toner image on a recording paper in an image forming apparatus such as a copying machine.

  In an image forming apparatus such as an electrophotographic copying machine, printer, facsimile, etc., a toner image formed on a photosensitive drum as an image carrier is transferred to a recording paper as a transfer material (recording medium), and heat is applied thereto. And a method of fixing to the recording paper by applying pressure.

  This fixing method includes an endless fixing belt that circulates as a heating member, and a pressure member (usually a roller) opposed to the fixing belt, and a fixing nip portion sandwiched between the fixing belt and the pressure member An unfixed recording paper is introduced and allowed to pass through, while heat from a radiant heat source provided inside the fixing belt, which is a heating member, and pressure by a pressure roller are applied to the recording paper, and a toner image is recorded on the recording paper. It is to be fixed to.

  Since the fixing belt, which is the heating member, is formed of a flexible sheet material, a support member for receiving the pressure of the pressure member is provided inside the fixing belt. The support member includes a sliding contact surface that is in sliding contact with the inner surface of the heating member, and the heating member slides along the sliding contact surface (see, for example, Patent Document 1 and Patent Document 2).

  Further, as the radiant heat source, for example, a halogen lamp is provided, and the heating member is heated by radiant heat from the halogen lamp. On the other hand, since the supporting member needs to have strength to withstand the pressure of the pressure roller, it is generally made of a metal material having a large size and a large heat capacity.

JP 2004-62053 A JP 2004-94146 A

  However, for example, when the above-described support member is a plate material, it is necessary to increase the plate thickness, and the heat capacity of the support member increases, so that the heat of the heated heating member is absorbed and the heat is deprived from the heating member. There is a problem that it ends up.

  As described above, when the heat of the heating member is taken away by the support member, a large amount of heat is required to raise the temperature of the heating member to a predetermined temperature, which causes energy saving problems and a problem that the warm-up time becomes long. There is. Further, since the heat of the heating member is taken away by the support member, there is a problem that sufficient heat cannot be transmitted to the surface of the recording paper and fixing failure occurs.

  The present invention considers the problems in the conventional fixing device described above, reduces the amount of heat taken away from the heating member as much as possible while maintaining the strength against the pressing force of the pressing member, thereby shortening the warm-up time and heating. The object is to make it difficult for fixing defects to occur due to shortage.

  In order to solve the above problems, the present invention employs the following configuration. That is, the fixing device according to the first aspect of the present invention includes a heating member having an endless metal sleeve as a base material, a radiation heat source provided in the heating member, and a slide that slides on the inner surface of the heating member. A supporting member having a moving surface; and a pressure roller that forms a nip portion that presses the heating member between the sliding surface of the supporting member and rotates the heating member in a predetermined direction. In a fixing device for fixing an unfixed image on a recording sheet through the nip portion, a backup member positioned on the opposite side of the sliding surface of the support member and receiving the pressure applied by the pressure roller applied to the support member And the contact surface of the backup member that contacts the support member is formed as an uneven surface.

  The second aspect of the present invention is the fixing device according to the first aspect of the present invention, wherein the uneven surface of the backup member is formed as an uneven surface having a plurality of spherical protrusions.

  The third aspect of the present invention is the fixing device according to the first aspect of the present invention, wherein the uneven surface of the backup member is formed as a plurality of rib-like protrusions extending in the rotation direction of the heating member.

  According to a fourth aspect of the present invention, there is provided a fixing device comprising: a heating member having an endless metal sleeve as a base material; a radiation heat source provided in the heating member; and a slide that slides on the inner surface of the heating member. A supporting member having a moving surface; and a pressure roller that forms a nip portion that presses the heating member between the sliding surface of the supporting member and rotates the heating member in a predetermined direction. In a fixing device for fixing an unfixed image on a recording sheet by passing through the nip portion, a backup member is provided on the side opposite to the sliding surface of the support member to receive the pressure applied by the pressure roller applied to the support member. A heat insulating member is interposed between the support member and the backup member.

  The fifth aspect of the present invention is the fixing device according to the fourth aspect of the present invention, wherein the heat insulating member suitably uses a heat resistant resin or silicon rubber.

  According to a sixth aspect of the present invention, the backup member has an inverted T-shaped cross section in which a plate-like rib perpendicular to the plate-like member is integrally provided on the back side of the plate-like member whose surface is in contact with the heating member. The fixing device according to any one of the first to fifth aspects of the present invention is formed.

  According to the present invention, while maintaining the strength against the pressing force of the pressure member, the amount of heat taken away from the heating member is reduced as much as possible, thereby shortening the warm-up time and making it difficult to cause poor fixing due to insufficient heating. I can do it.

1 is a front view schematically showing an outline of an image forming apparatus. FIG. 2 is a front view schematically illustrating a configuration of a fixing device. It is a perspective view of a support member and a backup member. It is a perspective view of a backup member. It is a perspective view of the backup member showing different embodiment. It is an enlarged view of the fixing device showing a different embodiment. It is a typical front view of the conventional apparatus used in the Example. It is a typical front view of the apparatus used in the Example. It is a graph showing a temperature measurement result.

  Hereinafter, an embodiment of an image forming apparatus including the fixing device according to the present invention will be specifically described.

  FIG. 1 illustrates the configuration of a copying machine that is an image forming apparatus. The image forming apparatus 1 includes a photosensitive drum 2 that is an image carrier, and a transfer belt 3 that conveys a recording sheet (transfer material) S is provided below the photosensitive drum 2. The photosensitive drum 2 is obtained by coating a surface of a metal drum with a layer of a photoreceptor, and is a drum having a diameter of 80 mm using, for example, an A-SI photoreceptor, and rotates in the direction of arrow A in the figure.

  A main charger 4 for uniformly charging the surface of the photosensitive drum 2, a laser irradiation device 5 for irradiating a photosensitive laser beam, and a developing unit 7 are arranged along the rotation direction on the outer periphery of the photosensitive drum 2. Are arranged in order. Note that a drum cleaner 9 and a static eliminator 10 for the photosensitive drum 2 are disposed downstream of the position (transfer portion) T where the photosensitive drum 2 and the recording sheet S conveyed by the transfer belt 3 are in contact with each other in the rotational direction. Is provided.

  The laser irradiation device 5 includes a laser emission unit and an optical device such as a mirror and a lens. The laser irradiation device 5 irradiates the surface of the photosensitive drum 2 with laser light in accordance with an image signal from a CCD camera not shown in FIG. An electrostatic latent image is formed on the surface of the photosensitive drum.

  The developing unit 7 is for attaching toner to a latent image formed on the surface of the photosensitive drum 2 to form a toner image. The developing unit 7 supplies an appropriate amount of toner in the toner container to the surface of the photosensitive drum, and this toner is exposed to light. It adheres only to the charged part of the drum 2 surface.

  The transfer belt 3 is an endless belt stretched between the driving roller 12 and the driven roller 13, and includes a NBR base material controlled in resistance to improve the recording paper adsorbability on the surface and the toner on the surface. In order to ensure releasability, a PTFE coating dispersed in a high-resistance urethane binder is applied.

  The drive roller 12 and the driven roller 13 are supported in parallel with each other in rotation axis and in parallel with the axis of the photosensitive drum 2. When the drive roller 12 is driven to rotate, the transfer belt 3 circulates in a predetermined direction (in the direction of arrow B in the figure) at a predetermined speed. The rotational speed (peripheral speed V2) of the photosensitive drum 2, the rotational speed (peripheral speed V12) of the driving roller 12, the moving speed (V3) of the transfer belt 3, and the recording paper S held on the transfer belt 3 by suction. The moving speeds (Vs) are all designed to be equal (V2 = V12 = V3 = Vs). In addition to the driving roller 12 and the driven roller 13, a belt cleaner 14 for removing excess toner adhering to the transfer belt 3 is provided downstream of the driving roller 12 in the belt moving direction. Further, a belt charger 18 for charging the belt and electrostatically adsorbing the recording paper S is provided on the upstream side of the transfer portion T of the transfer belt 3 in the moving direction, and downstream of the transfer position. A neutralizer 19 for removing the charging of the transfer belt is provided immediately before the drive roller 12.

  A bias applying transfer roller 15 is provided at a position facing the photosensitive drum 2 with the transfer belt 3 interposed therebetween. The transfer roller applies a charge having a polarity opposite to that of the toner on the surface of the photosensitive drum 2 to the transfer belt 3, and transfers the toner image on the photosensitive drum 2 to the recording paper S on the surface of the transfer belt 3 by this charge. A high voltage is applied from the high-voltage power supply 16 and the spring 17 is pressed against the back surface of the transfer belt 3.

  A fixing device 100 according to the present invention is provided on the downstream side in the moving direction of the recording paper S that is out of the drive roller 12.

  As shown in FIG. 2, the fixing device 100 includes a fixing belt 102 that is a heating member, a pressure roller 103 that is a pressure member, a support member 104, a heating source (heater) 105, and a backup member 106. ing. The fixing belt 102 is an endless flexible belt having moderate rigidity and elasticity. For example, the surface of a belt-like thin metal (nickel, stainless steel, etc.) is coated with fluorine. Those that have been applied can be suitably used.

  The fixing belt 102 circulates and moves on a substantially circular trajectory, and a heater 105 is installed therein as a radiant heat source. The heater 105 is for melting the toner on the recording paper S and securely adhering it to the recording paper. As the heater 105, for example, a halogen lamp is used.

  A support member 104 is disposed inside the annular fixing belt 102. The support member 104 is formed to have the same length as the width of the fixing belt 102 that is a heating member, and has a cross-sectional shape formed in a bowl shape having an upward concave shape, and a lower surface 104a serving as a pressure surface. The support member 104 is for maintaining the shape of the portion of the flexible fixing belt 102 facing the pressure roller 103 in a predetermined shape (in the illustrated example, a straight line) and securing a fixing nip portion. It is made of a material having rigidity, for example, a metal material such as stainless steel.

  A backup member 106 is provided on the back side (the upper side in the figure) of the support member 104. The backup member 106 is used to apply a back pressure so that the support member 104 can withstand the pressure of the pressure roller 103, and is made of a high strength material such as stainless steel, as shown in FIG. The plate-like member 106a facing the support member 104 and the rib-like member 106b rising at a right angle on the back side of the plate-like member 106a are formed in an inverted T-shaped cross section. The backup member 106 is attached to the machine frame (not shown) by the rib-like member 106b. By providing the backup member 106, the pressure of the pressure roller 103 can be withstood even if the support member 104 that contacts the fixing belt 102 as a heating member is downsized.

  A contact surface (lower surface in the figure) of the backup member 106 that contacts the support member 104 of the plate-like member 106a is formed as an uneven surface 106c. In FIG. 4, the uneven surface 106c is formed as a surface having a plurality of spherical protrusions 106d,. 5, the uneven surface 106c is formed by a plurality of rib-like protrusions 106e,... Along the rotation direction of the fixing belt 102 as a heating member (that is, the conveyance direction of the recording paper S).

  As described above, since the surface of the backup member 106 that contacts the support member 104 is formed as an uneven surface, the contact area between the two is reduced, and the amount of heat conduction from the support member 104 to the backup member 106 is reduced. The fixing belt 102 as a member is not easily deprived of heat. 5 is formed so as to be along the rotation direction of the fixing belt, that is, the moving direction of the recording paper S, the recording paper S can be smoothly conveyed.

  FIG. 6 shows an embodiment different from the above. In this embodiment, a heat insulating member 108 is interposed between the support member 104 and the backup member 106. Examples of the material of the heat insulating member 108 include polyetheretherketone (PEEK), polyimide (PI), polyamideimide (PAI), polybenzimidazole (PBI), polytetrafluoroethylene (PTFE), perfluoroalkoxyethylene (PFA), and the like. The heat resistant resin, silicon rubber, etc. can be used.

  The heat insulating member 108 is formed in a plate shape, and is fixed by a fixing means such as an adhesive while being sandwiched between the support member 104 and the backup member 106. In this case, the surface of the backup member 106 does not have to be an uneven surface, but it goes without saying that the surface may be an uneven surface.

  The pressure roller (pressure member) 103 is driven to rotate at a predetermined speed in the direction of the arrow X about the rotation shaft 107 by a driving device (not shown). When the pressure roller 103 rotates, the fixing belt 102 in contact with the pressure roller 103 is driven and rotated in the direction of the arrow Y in a rotating manner. A gap between the fixing belt 102 and the pressure roller 103 serves as a fixing nip portion 110 that presses the recording paper S.

  The recording paper S is a recording medium onto which an image has been transferred. The recording paper S is fed into the nip portion 110 from the front side of the fixing nip portion 110 and is conveyed in the arrow Z direction. On the front side and the rear side of the fixing nip portion 110, conveyance guides 111 and 112 for guiding the movement of the recording paper S are provided. Further, on the front side of the nip portion 110, a leading edge detecting means (a photoelectric sensor or the like) 115 for detecting the leading edge of the recording paper S is provided.

  Next, the operation of the image forming apparatus 1 in the illustrated example will be described. The image forming apparatus 1 is uniformly charged on the surface of the photosensitive drum 2 by the main charger 4 while being driven in synchronism so that the peripheral speed of the photosensitive drum 2 and the moving speed of the transfer belt 3 are the same. The laser irradiation device 5 scans the surface of the photosensitive drum with a laser beam that is turned on and off so as to correspond to a predetermined image, and forms a latent image in a charged state corresponding to the image signal on the surface of the photosensitive drum.

  The portion where the latent image is formed reaches the position of the developing unit 7 with the rotation of the photosensitive drum 2, where toner is supplied to the entire surface, but this toner is electrostatically attached to the surface of the photosensitive drum at the charged portion. , It does not adhere to uncharged parts.

  On the other hand, the recording sheet S as a transfer material is supplied onto the transfer belt 3 so as to be synchronized with the above operation. The recording paper S is fed in synchronization with the rotation of the photosensitive drum 2 while being electrostatically attracted to the belt 3 charged by the belt charger 18 so that the toner image is successfully transferred thereon. In the transfer portion T sandwiched between the photosensitive drum 2 and the transfer belt 3, the toner image is transferred to a predetermined location on the recording paper S. In this transfer portion T, since the reverse polarity charge is applied by the bias applying transfer roller 15, the toner image on the photosensitive drum 2 is transferred from the surface of the photosensitive drum 2 to the surface of the recording paper S. .

  The recording sheet S on which the image has been transferred is sent as it is in the direction of the arrow B by the transfer belt 3, but the transfer belt 3 is discharged by the charge eliminator 19 before the drive roller 12, so The transfer belt 3 is separated from the transfer belt 3 at a separation position where the transfer belt 3 changes its moving direction downward. The recording sheet S separated from the transfer belt 3 is sent to the fixing device 100 of the present invention.

  The recording sheet S supplied to the fixing device 100 passes through the conveyance guide 111 on the entrance side and is sent to the fixing nip portion 110 sandwiched between the fixing belt 102 as a heating member and the pressure roller 103 as a pressure member. , Pressure and heat are applied. Since the recording paper S that has passed through the fixing nip 110 is pressurized and heated in the nip 110, the toner adheres firmly to the recording paper S and the fixing is completed.

  In this fixing device 100, a support member 104 that receives the pressure of the pressure roller 103 and a backup member 106 that supports the support member from the back are provided inside the fixing belt 102, so that a stable fixing pressure is secured. can do. In addition, since the backup member 106 is provided, the support member 104 can be reduced in size, and the area where the fixing belt 102 receives radiant heat from the heater 105 can be increased, and the support can be achieved by the above-described reduction in size. Since the heat capacity of the member 104 is reduced, heat transfer from the fixing belt 102 to the support member can be reduced.

  Further, the contact surface between the support member 104 and the backup member 106 is formed as an uneven surface, or since the heat insulating member 108 is interposed between the support member 104 and the backup member 106, Heat transfer to the backup member 106 can be reduced. Therefore, the amount of heat taken away from the fixing belt 102 can be reduced also by this.

  In the fixing device shown in FIGS. 7 and 8, the effect of providing a heat insulating material was investigated. The fixing device shown in FIG. 7 represents a conventional device in which a support member 104 is provided but a backup member is not provided. The fixing device shown in FIG. 8 includes a support member 104 and a backup member 106. 1 represents an example of a device according to the present invention.

  A halogen heater (500 W + 600 W) is used as the heater (radiant heat source) 105, and a thickness of 0.03 mm and a diameter of 30 mm as the heating member (fixing belt) 102. A SUS belt having a length of 310 mm and having a release layer made of fluororesin PFA on the substrate surface was used. Further, the material of the support member 104 is SUS304, the thickness of the support member (A) in FIG. 7 is 1 mm, the heat capacity is 55.2 J / K, and the thickness of the support member 104 (B) in FIG. The heat capacity was 1 mm and 5.02 J / K. The material of the backup member 106 was SUS304, the thickness was 1.0 mm, and the heat capacity was 30.1 J / K. Further, the material of the pressure roller 103 is silicon rubber, the diameter is 25 mm, the length is 316 mm, the surface release layer is fluororesin resin (PFA), the core metal is iron, and the diameter is 12 mm. .

  7 and 8, the relationship between the temperature and the time at the temperature measurement point P was measured under the following conditions. Condition 1 (comparative example) is the conventional apparatus shown in FIG. 7, and condition 2 (comparative example) is the conventional apparatus shown in FIG. 7, in which a heat insulating member is provided between the support member 104 (A) and the heating member 102. The condition 3 (comparative example) remains the same as the apparatus shown in FIG. 8, and the condition 4 (example) is the same as the apparatus shown in FIG. 8 between the support member 104 (B) and the backup member 106. A heat insulating member is provided. As the heat insulating member, a 0.1 mm thick Teflon (PTFE) (registered trademark) tape was used. Further, a non-contact type sensor was used as the temperature sensor, and the pressure roller 103 started to rotate at the same time as the heat source (heater) was turned on.

  The relationship between the measured temperature and time was as shown in FIG. At the temperature measurement point P, the time required for the temperature to reach 180 ° C. after the heater was turned on was 27 seconds for Condition 1, 24 seconds for Condition 2, 11 seconds for Condition 3, and 8 seconds for Condition 4. From this result, it can be seen that Condition 4 in which the backup member 106 is provided and the support member 104 is downsized can raise the temperature to the predetermined temperature in the shortest time.

  The fixing device according to the present invention can be effectively used as a fixing device for an image forming apparatus such as an electrophotographic copying machine, a printer, or a facsimile.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Photosensitive drum 3 Transfer belt 4 Main charger 5 Laser irradiation apparatus 7 Developer 12 Drive roller 13 Drive roller 15 Bias application transfer roller 100 Fixing device 102 Fixing belt (heating member)
103 Pressure roller (Pressure member)
104 Support member 106 Backup member 108 Heat insulation member 110 Fixing nip portion

Claims (3)

  A heating member having an endless metal sleeve as a base material, a radiation heat source provided inside the heating member, a support member having a sliding surface sliding with an inner surface of the heating member, and A nip portion that presses the heating member between the sliding surface and a pressure roller that rotates the heating member in a predetermined direction, and passes an unfixed image on the recording paper through the nip portion. In the fixing device for fixing, a backup member that is positioned on the opposite side of the sliding surface of the support member and receives the pressure applied by the pressure roller applied to the support member is provided, and between the support member and the backup member A fixing device comprising a heat insulating member.   The fixing device according to claim 1, wherein the heat insulating member is a heat-resistant resin or silicon rubber.   The said backup member is formed in the cross-section reverse T-shape by which the plate-shaped rib at right angles to this plate-shaped member was integrally provided in the back side of the plate-shaped member which the surface contact | connects the said heating member. The fixing device according to 1.

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